As we reported back in December, Facebook recently unveiled a new Messenger app, which allowed users in some countries to quickly (and for no charge) send text messages to Facebook friends. It was effectively a runaround to text messaging. Now Facebook has introduced a free call functionality on the same Messenger app – boot the thing up, and you can call Facebook buddies over a Wi-Fi or cellular connection.

Some stipulations to note: According to Engadget, you've got to have the latest version of the iOS Messenger app to access the free calling feature, and so do the people you're trying to call. (Presumably an Android rollout is on the way.) In addition, as Terrence O'Brien of Engadget notes, since the "free call" button is tucked away on the "contact info" page of a profile, it does take a little bit of "probing" to discover which of your friends will accept Facebook calls.

"Call quality is remarkably good," O'Brien writes, "on par with a landline (yes some of us still talk on copper). Calls made over LTE [the new, fast cellular data connection] betrayed a touch more static and fuzz, but voices still came through crystal clear. While we would still like a better interface to see which of our Facebook friends we could call, we remain optimistic about the service. At first blush, it appears much easier to use than Skype or other VoIP services simply because the contacts list is already pre-populated with our pals."

For our part, we could find few friends that had an upgraded iOS app – it's possible our friends are just lazy so we didn't have a chance to extensively test out the software. But the calls we did place were, as O'Brien notes, surprisingly clear.

In related news, earlier this week, at a major press event at Facebook HQ, Facebook CEO Mark Zuckerberg took the wraps off Graph Search, a new search functionality which one reviewer has called "a never-ending path of quirky discovery." More here.